In communication system channels, noise generated by devices such as metal oxide semiconductor (MOS) devices, resistors, and bipolar junction transistors (BJTs) are generally modeled as Gaussian random noise, which has a probability density function (PDF) of a normal or Gaussian distribution and a colored or frequency dependent power spectral density (PSD). A communications channel may be modeled along with receiver circuitry in a simulation environment or using a hardware implementation.
While the design of many systems, such as communications systems, is designed to minimize the effects of noise, there are some applications in which Gaussian random noise is purposefully generated. For example, in the fields of data encryption, speech coding, Gaussian random noise may be generated to produce secure encryption keys and/or provide audio stimulus to digital filters to produce vocal sounds.
Noise generators may also be used to simulate the effects of additive noise generated in a communications channel and/or noise generated by the circuit devices present in a receiver and/or transmitter. Such simulated noise may be used to simulate the effect of noise in analog components of mixed signal systems such as phase locked loops (PLLs) and clock and data recovery (CDR) circuits. Modeling of the noise of a voltage controlled oscillator (VCO) may be performed to evaluate performance parameters such as period jitter and phase error. This modeling may be performed in a high level simulation environment such as MATLAB or System C.